The invention pertains to the identification and purging of air in a refrigerant handling system. More particularly, it pertains to a refrigerant air analyzer and purge system.
Air, or oxygen, is a major contaminant when it exists within a refrigerant system at levels as low as two percent. One major problem arising from air within a refrigerant system is the creation of higher than normal pressure levels within the system. This over-pressure situation over-taxes the system resulting in premature deterioration and failure of system components. Ultimately it also may create or enlarge a leak within the system.
The presence of air within the system can also create a problem due to moisture which is contained within the air. At expansion points within the system, the moisture drops out of the air in the form of ice crystals. The ice crystals collect at the expansion points and either slow or prevent the flow of refrigerant through the system. When the expansion valve warms, it melts the ice crystals and the refrigerant is again allowed to flow through the system unimpeded. However, this process continually repeats itself which causes intermittent cooling and inefficient operation of the system.
Also, refrigerant oil readily absorbs moisture and will pull moisture from the air contained within the system. This causes corrosion or the creation of a sludge which over time plugs strainers, expansion valves and capillary tubes making the system inoperable or less efficient. A need therefore exists to identify the presence of air and purge it from the refrigerant supply.
Additionally, due to the harmful effects of chlorofluorocarbon (CFC) refrigerant upon the ozone layer when it is released into the atmosphere, it is becoming common practice to recover and reuse refrigerant when servicing a system rather than vent it to the atmosphere and replace it with new refrigerant. The harmful effects of refrigerant have also decreased its availability. Recovery and reuse of refrigerant creates the potential for contamination of either a refrigerant supply tank or a refrigerant system if purification means such as those disclosed in U.S. Pat. Nos. 5,005,369; 5,172,562; 5,231,842; and 5,261,249 are not used. However, these purification means are expensive, bulky, and may needlessly be performed, which increases the cost and the time to service the unit when it may not even be contaminated. Therefore, a need exists to determine whether a source of refrigerant is contaminated with air or oxygen which can then be purged from the refrigerant prior to use.
Another source of contamination can result from the mixture of different types of refrigerants. There are various types of refrigerants such as R12, R22, R134a and R502. Each system is designed to operate with a specific type of refrigerant. When a different refrigerant or combination of refrigerants is introduced into the system, the system will not operate properly. To prevent contamination from other refrigerants, various techniques have been disclosed in U.S. Pat. Nos. 5,158,747; 5,295,360; and 5,371,019. These techniques identify the type of refrigerant contained within the system or supply tank, but they do not identify the amount or presence of air within the system or tank or purge the air from the system. Furthermore, their test chambers are enclosed, which necessitates evacuation of the test chamber for cleaning purposes prior to re-use in order to obtain accurate measurements, and makes them more difficult and less portable to use.
A significant obstacle exists in identifying or measuring the presence of air down to low levels, such as two percent, within a refrigerant system or a supply tank. This problem is created due to the excessive pressure that can exist within the system or the supply tank. The pressure, within the system or the supply tank, can reach levels of 500 pounds per square inch (psi) or greater, but a standard oxygen sensor with sufficient sensitivity to measure the destructive low levels of oxygen is only capable of operating up to a pressure level which is significantly less than 500 psi. Therefore, it is necessary to protect the oxygen sensor from excessive pressure levels.
One solution used in evacuation of a refrigerant system is to monitor the pressure level of the refrigerant system and once the pressure level of the system is sufficiently low, to open a solenoid valve. Opening the solenoid value will release refrigerant across another sensor which is more sensitive to lower pressure levels. The more sensitive pressure sensor monitors the pressure level until it meets a minimal threshold level identifying the completion of the evacuation process. This technique is disclosed in U.S. Pat. Nos. 4,441,330; 4,470,265 and 5,172,562 ('562 patent). These known devices describe a refrigerant recovery or recharging system but do not expose their respective pressure sensors to the refrigerant supply until the pressure level is sufficiently low, around 40 psi as disclosed in the '562 patent. However, attaining a pressure level this low before measuring for oxygen would necessitate nearly emptying the system prior to taking an oxygen measurement. Such a procedure would not only defeat the purpose of analyzing the entire supply, but would create inaccurate measurements that are taken in an inefficient manner to assess the air contamination of the entire system.
A second solution to creating a robust, sensitive sensor, would be to use an advanced oxygen sensor capable of accurate measurements in environments ranging from around 20 psi to over 500 psi. However, this technique would significantly increase the production costs, making the sensor not cost effective. Thus, there exists no known device to accurately detect and purge the presence of air from within a refrigerant system or supply that is self-contained, portable, robust and economically priced.